1. Field of the Invention
The present invention relates to a disk apparatus for recording/reproducing information data onto/from an optical disk, particularly capable of setting up the rotation of the optical disk mounted on the disk apparatus soon for shifting to a reproducing operation even if the optical disk may have a large weight.
2. Description of the Prior Art
Commercial optical disks such as DVDs (Digital Versatile Disks) and CDs (Compact Disks) generally have a diameter of 12 cm or 8 cm and vary in weight due to disk type and/or material (e.g. polycarbonate, PMMA (polymethylmetacrylate)), etc. even if the standards may be met. Also, some commercial optical disks are not up to the standards. Further, if a user sticks a label on an optical disk for identification of the optical disk, the weight of the optical disk is increased by the weight of the label. FIG. 4 is an illustrative view showing the change in the rotational frequency of an optical disk due to the weight thereof. When a constant voltage V1 is applied to a spindle motor for rotating an optical disk to set up the rotation of the optical disk, the setup time for the rotation of an optical disk B that has a larger weight than a reference optical disk A is longer than that of the reference optical disk A as shown in FIG. 4. Therefore, if an optical disk mounted on a disk apparatus has a large weight, when setting up the rotation of the optical disk to reproduce information data recorded on the optical disk, it takes the rotational frequency of the optical disk a long time to reach a predetermined rotational frequency R0, resulting in a problem in that it also takes a long time to start the reproduction from the optical disk.
As a background art, there is known a method of: measuring the time from the setup of the rotation of a spindle motor until the rotation is stabilized; determining the weight of an optical disk based on the difference between the measured time and a reference time; and, if the optical disk is heavier or lighter than a reference disk, setting the optical disk reading speed within an allowable error range from a reference rotational frequency (refer to Japanese Patent Laid-Open Publication No. 2004-310846 for example).
There is also known a method of: detecting the rotational frequency of a spindle motor when setting up the rotation of an optical disk; calculating the change of the rotational frequency based on the detection result to determine the weight ratio of the optical disk; and setting a servo gain according to the weight ratio of the optical disk (refer to Japanese Patent Laid-Open Publication No. Hei 10-293960 for example).
There is further known a method of: measuring the gravimetrical factor of an optical disk; deciding the level and time of a reverse voltage to be applied to the spindle motor based on the measurement result; and applying the reverse voltage to the spindle motor to decelerate or stop the rotation of the optical disk (refer to Japanese Patent Laid-Open Publication No. 2001-155417 for example).
However, although the first one among the above-described background arts allows for: measuring the time from the setup of the rotation of a spindle motor until the rotation is stabilized; determining the weight of an optical disk based on the difference between the measured time and a reference time; and, if the optical disk is heavier or lighter than a reference disk, setting the optical disk reading speed within an allowable error range from a reference rotational frequency, the method is intended only to set the optical disk reading speed suitably for the mounted optical disk by confirming whether or not the optical disk is heavier or lighter than the reference disk before starting a reproducing operation for the optical disk, but to solve the above-described problem.
Although the next one allows for: detecting the rotational frequency of a spindle motor when setting up the rotation of an optical disk; calculating the change of the rotational frequency based on the detection result to determine the weight ratio of the optical disk; and setting a servo gain according to the weight ratio of the optical disk, the method is intended only to drive the spindle motor at a minimum current consumption according to the weight of the optical disk, but to solve the above-described problem.
Although the further next one allows for: measuring the gravimetrical factor of an optical disk; deciding the level and time of a reverse voltage to be applied to the spindle motor based on the measurement result; and applying the reverse voltage to the spindle motor to decelerate or stop the rotation of the optical disk, the method is intended only to absorb the variation of optical disk weight, variation of the power supply voltage for driving the spindle motor, and variation of the spindle motor to stop the rotation of the optical disk, but to solve the above-described problem.